A variety of deckle systems are known for extrusion dies. A deckle system defines the width of the extrudate, as is well known to people skilled in this area of technology. The deckles on an extrusion die may be internal, external, or both.
One problem with conventional deckle systems is that cleaning may require substantial time and effort. For example, the operator may need to spend long periods of time taking apart the deckle system, and removing it from the die, before it is possible to clean the transition zone connecting the preland channel and the final land channel. Depending on the particular die/deckle being used, it may take on the order of 1-2 hours to perform a single cleaning. Given the importance of lean production in today's manufacturing environment, the need to disassemble a deckle prior to cleaning is a considerable drawback.
With respect to external deckles, U.S. Pat. Nos. 3,797,987 and 5,830,391 show external deckles where a sealing bar is pressed against, and thereby blocks, the die orifice. The sealing bar, however, does not extend into the orifice or into the final land channel. Instead, the sealing bar is merely seated against the outside of the orifice. As a consequence, the results achieved with external deckles of this nature may be less than ideal.
With respect to internal deckles, the conventional mechanisms that are used to adjust the positioning of internal deckles could be improved in many cases. For example, it would be desirable to provide deckle adjustment mechanisms that can provide relatively rapid travel of an internal deckle during adjustment.
Further, it is common to have an internal deckle blade that defines an internally threaded bore adapted to receive an externally threaded control shaft. While this arrangement has generally been acceptable, the internal threading of the deckle blade is sometimes damaged. If the damage is severe enough, then the whole deckle blade may need to be replaced, even though the rest of the deckle blade may be in good condition. Needless to say, this is wasteful and expensive.